Photoisomerization of Sultams Derived from Saccharin; Part 4: Generation of Cyclic Sulfine Hydroxamic Acids

Abstract

Various areno[d]annulated 3-mono-and 3,3-disubstituted 2,3-dihydro-[1,2]benzisothiazole 1,1-dioxides undergo a facile rearrangement into the corresponding 2,3-dihydro-2-hydroxy-[1,2]benzisothiazole 1-oxides upon irradiation at 254 nm in methanol. The latter represent a new, but labile functional group, i.e. the cyclic version of the sulfine hydroxamic acid. When C-3 in the starting materials is substituted by one methyl or phenyl only, that photoisomer is formed preferentially which has the sulfoxide O atom in an anti-orientation to the said substituent. 2-Alkoxymethyl substituted starting materials show the same type of formal oxygen shift. The structures of all photoproducts have been assigned largely from 1 H NMR data and unambiguously corroborated by X-ray crystal structure analyses of two photoproducts.

Structure and Photochemistry of a Saccharyl Thiotetrazole

“…The photochemistry of monomeric saccharin isolated in solid argon was recently investigated . A search in the literature also yielded some data regarding the photochemistry of some benzisothiazoles in solution, − indicating that the photoreactivity is determined by the structure of the saccharyl ring, the nature of substituents, and the reaction medium. By their turn, tetrazoles are known for their rich photochemistry both in solution and isolated in cryogenic matrices. , Generally, the photochemistry of tetrazole derivatives is influenced by the chemical nature and conformational flexibility of substituents, and when the molecule exhibits tautomerism, tautomer-selective photochemistry may take place. , …”

A novel photoisomerzation of 1,2‐benzothiazine 1,1‐dioxides to 1,3‐benzothiazine 1,1‐dioxides

“…Thus, photoexcited 3 first undergoes S-N bond homolysis [19][20][21][22][23] to give biradical 5 which can undergo cyclization to form a more stable captodative aziridine radical [24,25] 6 (R 1 = CO 2 Me, CN, COPh). Then, subsequent bond formation between S and C 3 gives rise the bicyclic intermediate 7.…”

Cyclic Sulfinamides

“…D. Döpp and co-workers conducted UV-induced photoisomerization of benzofused isothiazole 1,1-dioxides 182 into N-hydroxy sulfinamides 185 with the formal oxygen shift from the sulfur atom to the nitrogen one (Scheme 74). [116][117][118] The authors hypothesized that the reaction proceeds via conceivable intermediates 183 or 184 (formed after initial SÀ N bond homolysis).…”